1. Field of the Invention
The invention relates to an electric power steering system.
2. Description of the Related Art
In an electric power steering system, a drive controller that controls drive of an alternating-current motor is disposed at a position distant from the alternating-current motor, such as in a cabin of a vehicle, and the alternating-current motor and the drive controller are connected to each other by a cable. In such an electric power steering system, the weight increases due to the weight of the cable and the cable in some cases picks up noise and adversely affects the drive controller. In order to solve these problems, an electric power steering system has been developed in which a cable is shortened or eliminated by integrating the drive controller into the alternating-current motor. Specifically, there are available a system in which the drive controller is disposed at a rear end portion of a stator of the alternating-current motor and a system in which the drive controller is disposed between a stator and a worm speed reducing mechanism. See Japanese Patent Application Publication No. 2002-120739.
In the above-described electric power steering system, however, because a stator and a drive controller are coaxially arranged on the same axis as the rotation axis of the alternating-current motor, the amount of projection in the direction of the rotation axis of the alternating-current motor is large.